1. Field of the Invention
The present invention is in the fields of drug delivery, cancer treatment and diagnosis and pharmaceuticals. This invention provides a method of making antibody- or antibody fragment-targeted immunoliposomes for the systemic delivery of molecules to treat and image diseases, including cancerous tumors. The invention also provides immunoliposomes and compositions, as well as methods of imaging various tissues. The liposome complexes are useful for encapsulation of imaging agents, for example, for use in magnetic resonance imaging. The specificity of the delivery system is derived from the targeting antibodies or antibody fragments.
2. Background of the Invention
The ability to detect cancer, both primary and metastatic disease, at an early stage would be a major step towards the goal of ending the pain and suffering from the disease. The development of tumor targeted delivery systems for gene therapy has opened the potential for delivery of imaging agents more effectively than is currently achievable. Magnetic resonance imaging (MRI) can acquire 3-Dimensional anatomical images of organs. Coupling these with paramagnetic images results in the accurate localization of tumors as well as longitudinal and quantitative monitoring of tumor growth and angiogenesis. (Gillies, R. J., et al., Neoplasia 2:139-451 (2000); Degani, H., et al., Thrombosis & Haemostasis 89:25-33 (2003)).
One of the most common paramagnetic imaging agents employed in cancer diagnostics is Magnevist® (Gadopentetate Dimeglumine) (Mag) (Berlex Imaging, Montville, N.J.). Gadolinum is a rare earth element. It shows paramagnetic properties since its ion (Gd++) has seven unpaired electrons. The contrast enhancement observed in MRI scans is due to the strong effect of Gd++ primarily on the hydrogen-proton spin-lattice relaxation time (Ti). While free gadolinium is highly toxic, and thus unsuitable for clinical use, chelation with diethylenetriamine pentacetic acid (DTPA) generates a well tolerated, stable, strongly paramagnetic complex. This metal chelate is metabolically inert. However, after i.v. injection of gadopentetate dimeglumine, the meglumine ion dissociates from the hydhophobic gadopentetate, which is distributed only in the extracellular water. It cannot cross an intact blood-brain barrier, and therefore does not accumulate in normal brain tissue, cysts, post-operative scars, etc, and is rapidly excreted in the urine. It has a mean half-life of about 1.6 hours. Approximately 80% of the dose is excreted in the urine within 6 hours.
However, there are significant limitations with current contrast media, including that they are mainly based on perfusion and diffusion labels, and glucose uptake. With these free (non-complexed) agents, changes are seen in tumors, in inflammatory disease, and even with hormonal effects (in breast) (e.g. most gadolinium based and iodine based contrast agents document perfusion and diffusion into interstitial space, FDG-PET demonstrates glucose uptake). Thus, tumors are not specifically targeted by these contrast agents. In addition, active benign processes cannot always be separated from malignant, e.g. benign enhancing areas on breast MRI, chronic pancreatitis vs pancreatic carcinoma. There is also insufficient uptake by small tumors of these agents, and thus poor sensitivity and lack of early detection which is particularly critical in diseases like lung cancer. It may not be possible to detect solitary pulmonary nodules or pleural nodules. What is a needed, therefore, is a mechanism for delivering such agents to specific tissues within the body, for example, to tumor tissues and metastases.